Thermoplastic polyolefin compositions are actively pursued as alternative materials for fabricated articles made of polyvinyl chloride, thermoplastic polyurethane, and/or recycled polymers. In the automotive field, thermoplastic polyolefin compositions have been used for the fabrication of articles such as interior sheathing, including instrument panel skins, door panels, air bag covers and seat covers. Many of these articles have surface appearances and designs with complex surface characteristics, such as contours and geometric technical grains.
Rotational molding processes involving a rotating mold have been found to be useful in the production of a variety of molded articles. Slush molding is a type of rotational molding wherein less than the entire interior surface of the rotating mold is heated. That is, in a slush molding process, a preheated mold is in continuous contact with a reservoir holding unheated polymer powder. As the polymer powder contacts the heated mold surface, it melts and fills all aspects of the mold. The relevant portion of the mold surface must therefore be heated to a temperature sufficient to obtain a desirable melt viscosity in the polymer to be molded.
Slush molding processes have been found to be particularly advantageous for the production of molded articles with complex surface characteristics. Ideally, a slush molding composition needs to have good melt flow (low melt viscosity at molding temperatures) as well as little or no degradation at slush molding temperatures. It is important that the surface of the molded article be capable of withstanding the wear and tear associated with use of the article. Specifically, it is essential that the molded article have robust scratch and mar properties.
There is thus a need in the art for a thermoplastic polyolefin composition having good melt flow, little or no degradation during molding and good scratch and mar properties